Polishing pad and polishing method

ABSTRACT

A polishing pad and a polishing method are described. The polishing pad is made from a composition compresing a polymeric matrix, an additive, and a rheology altering agent. The rheology altering agent enables a uniform distribution of the additive in the polymeric matrix.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 96151047, filed on Dec. 28, 2007. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing pad and a polishing method. More particularly, the present invention relates to a polishing pad characterized by favorable uniformity and a polishing method with use of said polishing pad.

2. Description of Related Art

As devices of the industry progressing to more sophisticated and stringent, it is rather imperative to have smooth surfaces of wafers or substrates when integrated circuit devices or other devices are fabricated, such that the reliability of the devices can be ensured.

Chemical mechanical polishing (CMP) is one of the planarization technologies widely used in the industry. A polishing pad used in the CMP process is mainly made of polymer materials. The polishing pad is typically fabricated through mixing certain compositions and then initiating polymerization. During the mixing process, the compositions can be uniformly distributed generally. However, after the mixing process is stopped, certain compositions may agglomerate when the compositions are stored or during the process of forming the polishing pad, such that the uniform distribution of the compositions during the mixing process cannot remain. The uniformity of the polishing pad formed after polymerization is thereby affected.

As such, a relatively uniform polishing pad is needed to satisfy the industrial requirements.

SUMMARY OF THE INVENTION

The present invention is directed to a polishing pad containing a composition which contributes to favorable uniformity.

The present invention is further directed to a polishing method with use of a polishing pad containing a uniformly-distributed composition for accomplishing satisfactory polishing performance.

The present invention provides a polishing pad containing a composition in which a polymeric matrix, an additive, and a rheology altering agent are included. The additive is selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof. The rheology altering agent has a structure selected from a group consisting of hydrogen bond bonding, association, spatial orientation, and a combination thereof.

The present invention further provides a polishing pad containing a composition in which a polymeric matrix, an additive, and a rheology altering agent are included. The additive is selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof. The rheology altering agent enables the composition to have low viscosity at a shear rate higher than a transitional shear rate and to have high viscosity at a shear rate lower than the transitional shear rate.

The present invention further provides a polishing pad containing a polymeric matrix, a network structure constructed by a rheology altering agent in the polymeric matrix, and an additive selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof distributed in the polymeric matrix.

The present invention further provides a polishing method suitable for polishing a substrate. First, a polishing pad is provided. Next, a pressure is applied to a substrate to press the substrate onto the polishing pad. The substrate and the polishing pad are then moved relatively. The polishing pad contains a composition in which a polymeric matrix, an additive, and a rheology altering agent are included. The additive is selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof. The rheology altering agent has a structure selected from a group consisting of hydrogen bond bonding, association, spatial orientation, and a combination thereof.

The present invention further provides a polishing method suitable for polishing a substrate. First, a polishing pad is provided. Next, a pressure is applied to a substrate to press the substrate onto the polishing pad. The substrate and the polishing pad are then moved relatively. The polishing pad contains a composition in which a polymeric matrix, an additive, and a rheology altering agent are included. The additive is selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof. The rheology altering agent enables the composition to have low viscosity at a shear rate higher than a transitional shear rate and to have high viscosity at a shear rate lower than the transitional shear rate.

The present invention further provides a polishing method suitable for polishing a substrate. First, a polishing pad is provided. Next, a pressure is applied to a substrate to press the substrate onto the polishing pad. The substrate and the polishing pad are then moved relatively. The polishing pad contains a polymeric matrix, a network structure constructed by a rheology altering agent in the polymeric matrix,and an additive selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof distributed in the polymeric matrix.

The composition of the polishing pad in the present invention is uniformly distributed, so as to improve the uniformity of the polishing pad and achieve favorable polishing performance.

In order to make the aforementioned and other objects, features and advantages of the present invention more comprehensible, several embodiments accompanied with figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIGS. 1A through 1C are schematic cross-sectional views illustrating a polishing pad according to an embodiment of the present invention.

FIG. 2 is a curve illustrating variations in viscosity of a composition of a polishing pad of the present invention at different shear rates after a rheology altering agent is added to the composition.

DESCRIPTION OF EMBODIMENTS

The present invention is directed to a polishing pad in which a composition having an additive of different densities is provided. The present invention provides a composition to make the additive be uniformly distributed in the polymer matrix, even though the additive is intrisically not easy to be distributed in the polymer matrix due to the difference in the density. The polishing pad includes the polymeric matrix, the additive, and a rheology altering agent. The weight percentage of the additive in the composition of the polishing pad ranges from 0.1% to 30%, while the weight percentage of the rheology altering agent in the composition ranges from 0.5% to 30%. According to an embodiment of the present invention, the weight percentage of the additive in the composition ranges from 1% to 20%, while the weight percentage of the rheology altering agent in the composition ranges from 2% to 20%.

The polymeric matrix is, for example, polyester, polyether, polyurethane, polycarbonate, polyacrylate, polybutadiene, or other polymeric matrixes formed by polymerizing appropriate thermosetting resin or thermoplastic resin.

The additive is selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof. In comparison with the density of a typical polymeric matrix (approximately 0.8˜2.3 g/cm³), the density difference between the additive and the polymeric matrix is greater than 20% of the density of the polymeric matrix. For example, density difference may reach 50% of the density of the polymeric matrix.

The density of the low-density additive approximately ranges from 0.001 g/cm³ to 1.0 g/cm³. The low-density additive is, for example, a microsphere, a non-reactive gas, or a foaming agent. The microsphere is, for example, a hallow micro-balloon, such as Advancell® (made by Sekisui Chemical Company), Expancel® (made by Akzo Nobel), or the like. In an alternative, the microsphere is a liquid core micro-capsulate, such as Hydrocapsule® (made by Analytical Research Systems, INC). The non-reactive gas is, for example, carbon dioxide, dry air, nitrogen gas, or argon gas. The foaming agent includes an inorganic foaming agent or an organic foaming agent. The inorganic foaming agent is, for example, water, and the organic foaming agent is, for example, propane, butane, pentane, dichloromethane, hydrochlorofluorocarbons (such as HCFC-22, HCFC-141b, and so on), or hydrofluorocarbons (such as HFC-134a, HFC-365mfc, HFC-227ea, HFC-245fa, and so on).

The density of the high-density additive approximately ranges from 1.2 g/cm³ to 8.0 g/cm³. The high-density additive is, for example, abrasive particles, such as aluminum oxide particles, fumed or colloidal silicon oxide particles, cerium oxide particles, ceramic particles, diamond particles, or other appropriate abrasive particles, such that a fixed abrasive polishing pad in which the abrasive particles are added to the polymeric matrix is formed.

The rheology altering agent has a structure selected from a group consisting of hydrogen bond bonding, association, spatial orientation, and a combination thereof. Besides, the rheology altering agent forms a network structure in the polymeric matrix for uniformly distributing the additive. In some circumstances, the network structure may also be named a netted structure, a cage structure, and so on. Moreover, the rheology altering agent enables the composition of the polishing pad to have low viscosity at a shear rate higher than a transitional shear rate and to have high viscosity at a shear rate lower than the transitional shear rate.

In particular, the rheology altering agent and a precursor fluid of the polymeric matrix structurally interact and thereby the fluid is characterized by pseudoplasticity and thixotropy. Alternatively, the rheology altering agent contributes to increasing the viscosity of the fluid in a still state. Thereby, the rheology altering agent can adjust the Theological characteristics and the viscosity of the fluid. In some cases, the rheology altering agent is referred to as a thickener, an anti-settling agent, a rheology modifier, a rheological additive, or a thixotropic agent. In the present invention, the rheology altering agent of the composition of the polishing pad can be divided into an inorganic rheology altering agent and an organic rheology altering agent.

The descriptions of the inorganic rheology altering agent and the organic rheology altering agent will be provided hereinafter, respectively. Person skilled in the art should be able to embody the present invention based on the following descriptions, whereas the scope of the present invention is not limited thereby.

Inorganic Rheology Altering Agent

The inorganic rheology altering agent includes an oxide material having hydroxyl functional groups (M-OH) on its surface. In addition, the amount of the hydroxyl functional groups (M-OH) in a unit surface area of the inorganic rheology altering agent ranges from 0.5 M-OH/nm² to 2 M-OH/nm². The oxide material is a compound represented by M_(x)O_(y), wherein M is selected from a group consisting of silicon, aluminum, titanium, zirconium, cerium, magnesium, calcium, and a combination thereof. Taking silicon oxide as an example, some of silicon atoms are connecting to hydroxyl functional groups (—OH), so as to form a silanol groups (Si—OH) among which hydrogen bonds are bonded and a network structure is formed. Thereby, suspension or precipitation of the additive is reduced, such that the additive in the composition of the polishing pad can be uniformly distributed.

Moreover, in another embodiment, the inorganic rheology altering agent includes phyllosilicate, such as magnesium silicate (MgSiO₃), having hydroxyl functional groups (—OH) on its surface. After the MgSiO₃ is added and thoroughly distributed in the fluid, the hydrogen bonds are bonded among the hydroxyl functional groups (—OH), and the network structure is formed. Thereby, suspension or precipitation of the additive is reduced. As a result, the additive in the composition of the polishing pad can be uniformly distributed.

Organic Rheology Altering Agent

The organic rheology altering agent is mainly divided into an emulsifier, a swellable emulsion, a polyurethane thickener, and a hydrophobically modified polyether polyol.

The emulsifier is selected from a group consisting of a cationic emulsifier, an anionic emulsifier, and a non-ionic emulsifier. The use of the non-ionic emulsifier is a preferred embodiment. The non-ionic emulsifier is selected from a group consisting of fatty acid ester, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, polyglycerin, sorbitol, pentaerythritol, glyceride, sucrose, fatty amine, fatty acyl amine, polyglycerol ether, polypropylene glycol ether, and a combination thereof. The polyglycerol ether can be the polyglycerol ether of fatty acid ester, for example, glyceride, sorbitol ester, and so on.

The swellable emulsion is a hydrophobically modified alkali swellable emulsion (HASE), for example. The HASE, an associative thickener, is capable of achieving an alkaline swelling effect. That is to say, molecular chains of the HASE are extended in an alkaline condition, thus giving rise to a formation of the network structure. Hence, the HASE contributes to thickening function.

The polyurethane thickener is, for example, a hydrophobically modified ethylene oxide polyurethane (HEUR). The HEUR, an associative thickener, appears to be smoggy and easily-dispensed. As such, the HEUR is often applied to a non-solvent system. Meanwhile, the HEUR is a polymer having low molecular weight and made of polyethylene glycol, and the structure of HEUR usually has carbamate functional groups connecting to polyethylene glycol units with different chain lengths (. Besides, terminals of the HEUR contain hydrophobic functional groups. Therefore, the HEUR, with non-ionic characteristics, is able to form the network structure in the fluid, even though the alkaline environment is not given. Moreover, the hydrophobic functional groups can be bonded to each other.

The hydrophobically modified polyether has similar properties to the HASE and the HEUR. The hydrophobic functional groups contained in the hydrophobically modified polyether are capable of performing association, so as to form the network structure and accomplish the thickening effect.

Moreover, the organic rheology altering agent can be a long chained compound having polar functional groups, and the compound is selected from a group consisting of an acylamide compound, an amide compound, a carbamide compound, a carbamate compound, and a combination thereof. An average molecular weight of the compound ranges from 5000 to 500000, e.g., 50000˜200000. For example, the compound containing the polar functional groups may adopt BYK® series (BYK-Chemie) as the rheology altering agent, such as BYK®-410, containing urea/urethane functional groups. Through adding the BYK®-410 to the fluid, the network structure can be formed due to the spatial orientation. Thereby, with the network structure formed due to the spatial orientation constructed by the rheology altering agent, suspension or precipitation of the additive is reduced, and thus the additive in the composition of the polishing pad can be uniformly distributed.

Next, the composition of the polishing pad which is applied to a method of forming the polishing pad is described. Person skilled in the art should be able to embody the present invention based on the following descriptions elaborating the characteristics of the composition of the polishing pad in the present invention during the formation of the polishing pad, whereas the scope of the present invention is not limited thereby. FIGS. 1A through 1C are schematic cross-sectional views illustrating a polishing pad according to an embodiment of the present invention. FIG. 2 is a curve illustrating variations in viscosity of a composition of a polishing pad of the present invention at different shear rates after a rheology altering agent is added to the composition.

First, the precursor fluid of the polymeric matrix, the additive, and the rheology altering agent are mixed and stirred to form a fluid mixture of the composition of the polishing pad. The precursor fluid of the polymeric matrix is selected from ester, ether, urethane, carbonate, acrylate, butadiene, or other appropriate thermosetting resin or thermoplastic resin. The additive is selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof. The rheology altering agent is selected from the aforesaid inorganic rheology altering agent or the aforesaid organic rheology altering agent. In an embodiment of the present invention, the rheology altering agent has a structure selected from a group consisting of hydrogen bond bonding, association, spatial orientation, and a combination thereof.

In addition, as shown in FIG. 2, the rheology altering agent enables the fluid mixture to have low viscosity at a shear rate higher than a transitional shear rate 210 and to have high viscosity at a shear rate lower than the transitional shear rate 210. For example, the viscosity of the fluid mixture at the shear rate lower than the transitional shear rate 210 is two times or even more than five times the viscosity of the fluid mixture at the shear rate higher than the transitional shear rate 210. After stirring at the shear rate higher than the transitional shear rate 210, the additive and the rheology altering agent are uniformly distributed in the fluid mixture. The rheology altering agent forms the network structure after the stirring operation is completed. Alternatively, the viscosity of the fluid mixture is increased posterior to the termination of the stirring operation. Said characteristics of the rheology altering agent reduce the suspension of the low-density additive at an upper level and the precipitation of the high-density additive at a lower level. Therefore, when the composition is stored or during a process of forming the polishing pad, the additive can still be uniformly distributed in the fluid mixture. In one embodiment of the present invention, the transitional shear rate ranges from 5 rpm to 20 rpm. The viscosity of the fluid mixture at a shear rate lower than the transitional shear rate (e.g. 2 rpm) or in a still state is ten times or more than ten times the viscosity of the fluid mixture at a shear rate higher than the transitional shear rate (e.g. 100 rpm). Note that the range of the transitional shear rate often varies upon the amount of the composition or the dimension of a mixing tank used herein. However, the mostly employed mixing equipment in the industry can usually achieve a shear rate equal to or higher than 1000 rpm, which exceeds the transitional shear rate of the present embodiment. The varying characteristics of the rheology altering agent are elaborated by way of the relation between viscosity and shear rate, while the scope of the present invention is not limited thereby. Namely, person skilled in the art should be able to embody that said characteristics can also be demonstrated by means of the relation between shear force and shear rate, or between viscosity and mixing time when stirring operation at a fixed shear rate, and so on.

In light of the foregoing, when the fluid mixture of the composition of the polishing pad is stored, the viscosity of the fluid mixture can be reduced during the process of manufacturing the polishing pad as long as the stirring process is carried out at a shear rate higher than the transitional shear rate. Thereby, the fluid mixture is polymerized and solidified to form the polishing pad, such as formed in a mold. Since additive is isolated from each other by the network structure formed by the rheology altering agent, the additive can be uniformly distributed within the polymeric matrix of the polishing pad. The network structure formed by the rheology altering agent not only reduces suspension or precipitation of the additive because of difference in the density, but also reduces agglomeration of the additive. In other words, the density in different areas of the polishing pad of the present invention has less density variations than a polishing pad in which the additive is in the same amount but no rheology altering agent is formed. Besides, the additive of the polishing pad of the present invention is agglomerated to a less extent in comparison with a polishing pad in which the additive is in the same amount but no rheology altering agent is formed.

The composition of the polishing pad can be a mixture categorized into a single-liquid type reaction system, a dual-liquid type reaction system, or a multi-liquid type reaction system. In addition, the composition can also include a catalyst, a chain extender, or the like, which is well known to person skilled in the art. Subsequent processes of forming the polishing pad further includes planarizing a surface of the polishing pad to form a polishing layer, and grooves or surface patterns can optionally be formed on a polished surface of the polishing layer. Additionally, an affixing layer which can be securely attached to a polishing table is formed on a back surface of the polishing surface. In an alternative, a supporting layer which is relatively soft can be formed between the polishing layer and the affixing layer.

The finished polishing pad is illustrated in FIGS. 1A through 1C. For instance, with reference to FIG. 1A, a rheology altering agent 102 a forms the network structure in a polymeric matrix 100 a of the composition of a polishing pad 110. Thus, low-density additives 104 (e.g. hallow micro-balloons) can be uniformly distributed in the finished polishing pad 110. Besides, as shown in FIG. 1B, when the composition of a polishing pad 120 contains high-density additives 106 (e.g. cerium oxide abrasive particles), the network structure formed by a rheology altering agent 102 b in a polymeric matrix 100 b enables the high-density additives 106 to be uniformly distributed in the finished polishing pad 120. Likewise, as indicated in FIG. 1C, when the composition of a polishing pad 130 contains low-density additives 104 c and high-density additives 106 c, the network structure formed by a rheology altering agent 102 c in a polymeric matrix 100 c enables the low-density additives 104 c and the high-density additives 106 to be uniformly distributed in the finished polishing pad 130.

On the other hand, the polishing method provided by the present invention is suitable for polishing a substrate. First, a polishing pad formed by said composition is provided. Next, a pressure is applied to the substrate to press the substrate onto the polishing pad. Thereafter, the substrate and the polishing pad are moved relatively, such that a portion of a surface of the substrate is removed, and thereby the substrate is planarized.

On account of the uniformly distributed composition of the polishing pad, the polishing method disclosed in the present invention is able to achieve favorable polishing performance. Moreover, slurry or solution can be supplied in the polishing process according to the polishing method of the present invention, such that the polishing method turns out to be a chemical mechanical polishing (CMP) process.

To sum up, the composition of the polishing pad in the present invention is uniformly distributed, and thereby the uniformity of the polishing pad is improved. As the polishing pad having the uniformly distributed composition is employed in the polishing method of the present invention, favorable polishing performance can be accomplished.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents. 

1. A polishing pad having a composition comprising: a polymeric matrix; an additive selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof, and a rheology altering agent having a structure selected from a group consisting of hydrogen bond bonding, association, spatial orientation, and a combination thereof.
 2. The polishing pad as claimed in claim 1, wherein the density difference between the additive and the polymeric matrix is greater than 20% of the density of the polymeric matrix.
 3. The polishing pad as claimed in claim 1, wherein the low-density additive comprises a microsphere, a non-reactive gas, or a foaming agent.
 4. The polishing pad as claimed in claim 1, wherein the high-density additive comprises abrasive particles.
 5. The polishing pad as claimed in claim 1, wherein the rheology altering agent enables the composition to have low viscosity at a shear rate higher than a transitional shear rate and to have high viscosity at a shear rate lower than the transitional shear rate.
 6. The polishing pad as claimed in claim 1, wherein the rheology altering agent comprises an inorganic rheology altering agent.
 7. The polishing pad as claimed in claim 6, wherein the inorganic rheology altering agent comprises an oxide M_(x)O_(y) having hydroxyl functional groups (M-OH) on its surface, and M of said oxide M_(x)O_(y) is selected from a group consisting of silicon, aluminum, titanium, zirconium, cerium, magnesium, calcium, and a combination thereof.
 8. The polishing pad as claimed in claim 7, wherein the amount of the hydroxyl functional groups (M-OH) in a unit surface area of the inorganic rheology altering agent ranges from 0.5 M-OH/nm² to 2 M-OH/nm².
 9. The polishing pad as claimed in claim 6, wherein the inorganic rheology altering agent comprises phyllosilicate.
 10. The polishing pad as claimed in claim 1, wherein the rheology altering agent comprises an organic rheology altering agent.
 11. The polishing pad as claimed in claim 10, wherein the organic rheology altering agent comprises an emulsifier.
 12. The polishing pad as claimed in claim 11, wherein the emulsifier is selected from a group consisting of a cationic emulsifier, an anionic emulsifier, and a non-ionic emulsifier.
 13. The polishing pad as claimed in claim 10, wherein the organic rheology altering agent is selected from a group consisting of fatty acid ester, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, polyglycerin, sorbitol, pentaerythritol, glyceride, sucrose, fatty amine, fatty acyl amine, polyglycerol ether, polypropylene glycol ether, and a combination thereof.
 14. The polishing pad as claimed in claim 10, wherein the organic rheology altering agent comprises a long chained compound having a polar functional group, and the long chained compound is selected from a group consisting of an acylamide compound, an amide compound, a carbamide compound, a carbamate compound, and a combination thereof.
 15. The polishing pad as claimed in claim 14, wherein an average molecular weight of the compound ranges from 5000 to
 500000. 16. The polishing pad as claimed in claim 10, wherein the organic rheology altering agent comprises a swellable emulsion.
 17. The polishing pad as claimed in claim 16, wherein the organic rheology altering agent comprises a hydrophobically modified alkali swellable emulsion (HASE).
 18. The polishing pad as claimed in claim 10, wherein the organic rheology altering agent comprises a polyurethane compound.
 19. The polishing pad as claimed in claim 18, wherein the organic rheology altering agent comprises a hydrophobically modified ethylene oxide polyurethane (HEUR).
 20. The polishing pad as claimed in claim 10, wherein the rheology altering agent comprises a hydrophobically modified polyether compound.
 21. The polishing pad as claimed in claim 1, wherein the weight percentage of the additive in the composition ranges from 0.1% to 30%, while the weight percentage of the rheology altering agent in the composition ranges from 0.5% to 30%.
 22. A polishing pad having a composition comprising: a polymeric matrix; an additive selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof; and a rheology altering agent enabling the composition to have low viscosity at a shear rate higher than a transitional shear rate and to have high viscosity at a shear rate lower than the transitional shear rate.
 23. The polishing pad as claimed in claim 22, wherein the density difference between the additive and the polymeric matrix is greater than 20% of the density of the polymeric matrix.
 24. The polishing pad as claimed in claim 22, wherein the low-density additive comprises a microsphere, a non-reactive gas, or a foaming agent.
 25. The polishing pad as claimed in claim 22, wherein the high-density additive comprises abrasive particles.
 26. The polishing pad as claimed in claim 22, wherein the high viscosity is two times the low viscosity or more.
 27. The polishing pad as claimed in claim 22, wherein the rheology altering agent having a structure selected from a group consisting of hydrogen bond bonding, association, spatial orientation, and a combination thereof.
 28. The polishing pad as claimed in claim 22, wherein the rheology altering agent comprises an inorganic rheology altering agent.
 29. The polishing pad as claimed in claim 28, wherein the inorganic rheology altering agent comprises an oxide M_(x)O_(y) having hydroxyl functional groups (M-OH) on its surface, and M of the oxide M_(x)O_(y) is selected from a group consisting of silicon, aluminum, titanium, zirconium, cerium, magnesium, calcium, and a combination thereof.
 30. The polishing pad as claimed in claim 29, wherein the amount of the hydroxyl functional groups (M-OH) in a unit surface area of the inorganic rheology altering agent ranges from 0.5 M-OH/nm² to 2 M-OH/nm².
 31. The polishing pad as claimed in claim 28, wherein the inorganic rheology altering agent comprises phyllosilicate.
 32. The polishing pad as claimed in claim 22, wherein the rheology altering agent comprises an organic rheology altering agent.
 33. The polishing pad as claimed in claim 32, wherein the organic rheology altering agent comprises an emulsifier.
 34. The polishing pad as claimed in claim 33, wherein the emulsifier is selected from a group consisting of a cationic emulsifier, an anionic emulsifier, and a non-ionic emulsifier.
 35. The polishing pad as claimed in claim 32, wherein the organic rheology altering agent is selected from a group consisting of fatty acid ester, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, polyglycerin, sorbitol, pentaerythritol, glyceride, sucrose, fatty amine, fatty acyl amine, polyglycerol ether, polypropylene glycol ether, and a combination thereof.
 36. The polishing pad as claimed in claim 32, wherein the organic rheology altering agent comprises a long chained compound having a polar functional group, and the long chained compound is selected from a group consisting of an acylamide compound, an amide compound, a carbamide compound, a carbamate compound, and a combination thereof.
 37. The polishing pad as claimed in claim 36, wherein an average molecular weight of the compound ranges from 5000 to
 500000. 38. The polishing pad as claimed in claim 32, wherein the organic rheology altering agent comprises a swellable emulsion.
 39. The polishing pad as claimed in claim 38, wherein the organic rheology altering agent comprises a hydrophobically modified alkali swellable emulsion (HASE).
 40. The polishing pad as claimed in claim 32, wherein the organic rheology altering agent comprises a polyurethane compound.
 41. The polishing pad as claimed in claim 40, wherein the organic rheology altering agent comprises a hydrophobically modified ethylene oxide polyurethane (HEUR).
 42. The polishing pad as claimed in claim 32, wherein the rheology altering agent comprises a hydrophobically modified polyether compound.
 43. The polishing pad as claimed in claim 22, wherein the weight percentage of the additive in the composition ranges from 0.1% to 30%, while the weight percentage of the rheology altering agent in the composition ranges from 0.5% to 30%.
 44. A polishing pad, comprising: a polymeric matrix; a network structure constructed by a rheology altering agent in the polymeric matrix; and an additive distributed in the polymeric matrix, the additive being selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof.
 45. The polishing pad as claimed in claim 44, wherein the rheology altering agent having a structure selected from a group consisting of hydrogen bond bonding, association, spatial orientation, and a combination thereof.
 46. The polishing pad as claimed in claim 44, wherein the additive is isolated by the network structure.
 47. The polishing pad as claimed in claim 44, wherein the density in different areas of the polishing pad has less density variations than a polishing pad in which the additive is in the same amount but no rheology altering agent is formed.
 48. The polishing pad as claimed in claim 44, wherein the additive of the polishing pad is agglomerated to a less extent in comparison with a polishing pad in which the additive is in the same amount but no rheology altering agent is formed.
 49. A polishing method suitable for polishing a substrate, the polishing method comprising: providing a polishing pad; applying a pressure to a substrate to press the substrate onto the polishing pad; and relatively moving the substrate and the polishing pad, wherein the polishing pad has a composition comprising: a polymeric matrix; an additive selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof; and a rheology altering agent having a structure selected from a group consisting of hydrogen bond bonding, association, spatial orientation, and a combination thereof.
 50. A polishing method suitable for polishing a substrate, the polishing method comprising: providing a polishing pad; applying a pressure to a substrate to press the substrate onto the polishing pad; and relatively moving the substrate and the polishing pad, wherein the polishing pad has a composition comprising: a polymeric matrix; an additive selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof; and a rheology altering agent enabling the composition to have low viscosity at a shear rate higher than a transitional shear rate and to have high viscosity at a shear rate lower than the transitional shear rate.
 51. A polishing method suitable for polishing a substrate, the polishing method comprising: providing a polishing pad; applying a pressure to a substrate to press the substrate onto the polishing pad; and relatively moving the substrate and the polishing pad, wherein the polishing pad comprising: a polymeric matrix; a network structure constructed by a rheology altering agent in the polymeric matrix; and an additive distributed in the polymeric matrix, the additive being selected from a group consisting of a low-density additive, a high-density additive, and a combination thereof. 